1. Field of the Invention
The present invention relates to power converter systems, and more particularly to detection circuits and methods for monitoring power converter systems to identify faults.
2. Description of the Prior Art
Among the many fault conditions encountered by electronic power conversion systems, shoot-through and short circuit conditions are the most disastrous and which could destroy the system in microseconds. To protect the systems from these accidents, many fault detection techniques have been widely used. For example, a technique of desaturation detection is available that depends on the fact that the power converter device terminal voltage should be low when turned on. If it is not low, then either the gate drive is faulty or huge current is saturating the device. Current sensors could be used to detect over-current situations. However, the speed of such sensors is limited.
An example of a prior art technique for the protection of power converter systems from faults is disclosed in U.S. Pat. No. 4,958,121 issued Sep. 18, 1990 to Cuomo et al. entitled PROTECTION OF POWER CONVERTERS FROM VOLTAGE SPIKES.
In this patent a protection system for power converter systems is disclosed comprising a voltage spike sensing circuit for generating a logic signal in the presence of a voltage spike, and logic means responsive to the logic signal from the spike sensing circuit for opening a first analog switch and closing a second analog switch.
Other references of general interest include U.S. Pat. Nos. 5,528,446, 5,559,656, 5,596,466 and 5,687,049.
An object of the present invention is to provide a system for monitoring the switching spikes on the dc bus of a power converter to identify disastrous faults and out-of-range parameters. The system observes the height, width and shape of the spikes so that high-speed faults such as shoot-through or low-impedance short-circuit conditions can be detected immediately. Out of range series resistance due to rusty bolts, loosened screws, and a deteriorating or missing capacitor bank can be detected. Further, the switching speed of the active devices can be estimated by simple techniques.